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            <div class="section-title">
              <h1>Boost Library Requirements and Guidelines</h1>
            </div>

            <div class="section-body">
              <ul class="toc">
                <li><a href="#Introduction">Introduction</a></li>

                <li>
                  <a href="#Requirements">Requirements</a>

                  <ul>
                    <li><a href="#License">License requirements</a></li>

                    <li><a href="#Portability">Portability
                    requirements</a></li>

                    <li><a href="#Ownership">Ownership</a></li>

                    <li><a href="#Organization">Organization</a></li>

                    <li><a href="#Integration">Integration</a></li>
                  </ul>
                </li>

                <li>
                  <a href="#Guidelines">Guidelines</a>

                  <ul>
                    <li><a href="#Backwards_compatibility">Backwards Compatibility</a></li>
                    <li><a href="#Design_and_Programming">Design and
                    programming</a></li>

                    <li><a href="#Filenames">Filenames</a></li>

                    <li><a href="#Naming_consistency">Naming
                    consistency</a></li>

                    <li><a href="#Documentation">Documentation</a></li>
                  </ul>
                </li>

                <li>
                  <a href="#Rationale">Rationale</a>

                  <ul>
                    <li><a href=
                    "#Exception-specification">Exception-specification
                    rationale</a></li>

                    <li><a href="#Naming">Naming conventions
                    rationale</a></li>

                    <li><a href="#code_fonts">Source code fonts
                    rationale</a></li>

                    <li><a href="#Tabs">Tabs rationale</a></li>

                    <li><a href="#FileNamesRat">Directory and filename
                    rationale</a></li>

                    <li><a href="#JavaScript">ECMAScript/JavaScript
                    rationale</a></li>

                    <li><a href="#Rationale_rationale">Rationale
                    rationale</a></li>

                    <li><a href="#Acknowledgements">Acknowledgements
                    rationale</a></li>
                  </ul>
                </li>
              </ul>

              <h2><a name="Introduction" id=
              "Introduction"></a>Introduction</h2>

              <p>This page describes requirements and guidelines for the
              content of a library submitted to Boost.</p>

              <p>See the <a href="submissions.html">Boost Library Submission
              Process</a> page for a description of the process involved.</p>

              <h2><a name="Requirements" id=
              "Requirements"></a>Requirements</h2>

              <p>To avoid the frustration and wasted time of a proposed
              library being rejected, it must meet these requirements:</p>

              <ul>
                <li>The license must meet the <a href="#License">license
                requirements</a> below. Restricted licenses like the GPL and
                LGPL are not acceptable.</li>

                <li>The copyright <a href="#Ownership">ownership</a> must be
                clear.</li>

                <li>The library should be generally useful.</li>

                <li>The library must meet the <a href=
                "#Portability">portability requirements</a> below.</li>

                <li>The library should preferably meet the <a href=
                "#Organization">organization requirements</a> below. But is
                only required to meet them after acceptance.</li>

                <li>The library must come reasonably close to meeting the
                <a href="#Guidelines">Guidelines</a> below.

                  <ul>
                    <li><a href="#Design_and_Programming">Design and
                    Programming</a></li>

                    <li><a href="#Filenames">Filenames</a></li>

                    <li><a href="#Documentation">Documentation</a></li>
                  </ul>
                </li>

                <li>The author must be willing to participate in discussions
                on the mailing list, and to refine the library
                accordingly.</li>
              </ul>

              <p>There's no requirement that an author read the mailing list
              for a time before making a submission. It has been noted,
              however, that submissions which begin "I just started to read
              this mailing list ..." seem to fail, often embarrassingly.</p>

              <h3><a name="License" id="License"></a>License
              requirements</h3>

              <p>The preferred way to meet the license requirements is to use
              the <a href="../LICENSE_1_0.txt">Boost Software License</a>.
              See <a href="../users/license.html">license information</a>. If
              for any reason you do not intend to use the Boost Software
              License, please discuss the issues on the Boost <a href=
              "../community/groups.html#main">developers mailing list</a>
              first.</p>

              <p>The license requirements:</p>

              <ul>
                <li>Must be simple to read and understand.</li>

                <li>Must grant permission without fee to copy, use and modify
                the software for any use (commercial and
                non-commercial).</li>

                <li>Must require that the license appear on all copies of the
                software source code.</li>

                <li>Must not require that the license appear with executables
                or other binary uses of the library.</li>

                <li>Must not require that the source code be available for
                execution or other binary uses of the library.</li>

                <li>May restrict the use of the name and description of the
                library to the standard version found on the Boost web
                site.</li>
              </ul>

              <h3><a name="Portability" id="Portability"></a>Portability
              requirements</h3>

              <ul>
                <li>A library's interface must portable and not restricted to
                a particular compiler or operating system.</li>

                <li>A library's implementation must if possible be portable
                and not restricted to a particular compiler or operating
                system. If a portable implementation is not possible,
                non-portable constructions are acceptable if reasonably easy
                to port to other environments, and implementations are
                provided for at least two popular operating systems (such as
                UNIX and Windows).</li>

                <li>There is no requirement that a library run on C++
                compilers which do not conform to the ISO standard.</li>

                <li>There is no requirement that a library run on any
                particular C++ compiler. Boost contributors often try to
                ensure their libraries work with popular compilers. The
                boost/config.hpp <a href=
                "../doc/libs/release/libs/config/config.htm">configuration
                header</a> is the preferred mechanism for working around
                compiler deficiencies.</li>
              </ul>

              <p>Since there is no absolute way to prove portability, many
              boost submissions demonstrate practical portability by
              compiling and executing correctly with two different C++
              compilers, often under different operating systems. Otherwise
              reviewers may disbelieve that porting is in fact practical.</p>

              <h3><a name="Ownership" id="Ownership"></a>Ownership</h3>

              <p>Are you sure you own the library you are thinking of
              submitting? "How to Copyright Software" by MJ Salone, Nolo
              Press, 1990 says:</p>

              <blockquote>
                <p>Doing work on your own time that is very similar to
                programming you do for your employer on company time can
                raise nasty legal problems. In this situation, it's best to
                get a written release from your employer in advance.</p>
              </blockquote>

              <p>Place a copyright notice in all the important files you
              submit. Boost won't accept libraries without clear copyright
              information.</p>

              <h3><a name="Organization" id=
              "Organization"></a>Organization</h3>

              <p>The quality of the Boost libraries is not just about the
              APIs and code design. But also about presenting a consistent
              view to users of the libraries as a whole. Upon acceptance
              libraries must adhere to this directory and file structure:</p>

              <table summary="Boost standard library organization">
                <caption>
                  Boost standard library organization
                </caption>

                <thead>
                  <tr>
                    <th>Sub-directory or file</th>

                    <th>Contents</th>

                    <th>Required</th>
                  </tr>
                </thead>

                <tbody>
                  <tr>
                    <td><code>build</code></td>

                    <td>Library build files such as a Jamfile, IDE projects,
                    Makefiles, Cmake files, etc.</td>

                    <td>Required if the library has sources to build.</td>
                  </tr>

                  <tr>
                    <td><code>doc</code></td>

                    <td>Sources to build with and built documentation for the
                    library. If the library needs to build documentation from
                    non-HTML files this location must be buildable with Boost
                    Build.</td>

                    <td>Required for all libraries.</td>
                  </tr>

                  <tr>
                    <td><code>doc/html</code></td>

                    <td>Documentation (HTML) files.</td>

                    <td>Required for all libraries with pregenerated
                    documentation. And generated documentation must be
                    generated here.</td>
                  </tr>

                  <tr>
                    <td><code>example</code></td>

                    <td>Sample program files.</td>

                    <td>Required if library has sample files. Which is highly
                    recommended.</td>
                  </tr>

                  <tr>
                    <td><code>index.html</code></td>

                    <td>Redirection to HTML documentation. See <a href=
                    "#Redirection">"Redirection"</a> for a template for this
                    file.</td>

                    <td>Required for all libraries.</td>
                  </tr>

                  <tr>
                    <td><code>include/boost/<em>library</em></code></td>

                    <td>Header files for the library.</td>

                    <td>Required for all libraries.</td>
                  </tr>

                  <tr>
                    <td><code>meta</code></td>

                    <td>Meta-data about the library.</td>

                    <td>Required for all libraries.</td>
                  </tr>

                  <tr>
                    <td><code>meta/libraries.json</code></td>

                    <td><a title="Library Metadata File Format" href=
                    "library_metadata.html">A JSON file containing
                    information about the library</a> used to generate
                    website and documentation for the Boost C++ Libraries
                    collection.</td>

                    <td>Required for all libraries.</td>
                  </tr>

                  <tr>
                    <td><code>meta/explicit-failures-markup.xml</code></td>

                    <td>XML file describing expected test failures, used to
                    generate the test report.</td>

                    <td>Optional</td>
                  </tr>

                  <tr>
                    <td><code>src</code></td>

                    <td>Source files which must be compiled to build the
                    library.</td>

                    <td>Required if the library has source files to
                    build.</td>
                  </tr>

                  <tr>
                    <td><code>test</code></td>

                    <td>Regression or other test programs or scripts. This is
                    the <em>only</em> location considered for automated
                    testing. If you have additional locations that need to be
                    part of automated testing it is required that this
                    location refer to the additional test locations.</td>

                    <td>Required for all libraries.</td>
                  </tr>

                  <tr>
                    <td><code>tools</code></td>

                    <td>Tools used, or offered, by the library. The structure
                    within this is up to the library, but it's recommended to
                    use similar structure as a regular Boost library or
                    tool.</td>

                    <td>Required for libraries that have runable tools.</td>
                  </tr>
                </tbody>
              </table>

              <h3><a name="Integration" id="Integration"></a>Integration</h3>

              <p>Once a library is accepted as part of the Boost C++
              Libraries it is required that it integrate properly into the
              development, testing, documentation, and release processes.
              This integration increases the eventual quality of all the
              libraries and is integral to the expected quality of the whole
              of the Boost C++ Libraries from users. In addition to the
              <a href="#Organization">organization requirements</a> above the
              following integration is required:</p>

              <h4>Building Sources</h4>

              <p>The library needs to provide a Boost Build project that the
              user, and the top level Boost project, can use to build the
              library if it has sources to build. The Jamfile for the source
              build needs to minimally declare the project, the library
              target(s), and register the target(s) for installation. For
              example:</p>
              <pre>
project boost/my_lib ;

lib boost_my_lib : a.cpp ;

boost-install boost_my_lib ;
</pre>

              <h4>Testing</h4>

              <p>The library needs to provide a Boost Build project that the
              user, and the root Boost test script, can use to build and run
              the tests for the library. The testing build project must
              reside in the <tt>project-root/test</tt> directory and must be
              buildable from this or another directory (for example, <tt>b2
              libs/<em>library</em>/test</tt> from the Boost root must
              work.)</p>

              <p>An example <tt>test/Jamfile</tt> is given below:</p>
              <pre>
import testing ;

run default_constructor.cpp ;
run copy_constructor.cpp ;
compile nested_value_type.cpp ;
compile-fail invalid_conversion_1.cpp ;
</pre>

              <p><em>WARNING:</em> This is the only location considered for
              testing by the top level testing script. If you want to test
              additional locations you must declare such that they are built
              as dependencies or by using <tt>build-project</tt>.</p>

              <p>If the library requires a level of C++ conformance that
              precludes certain compilers or configurations from working,
              it's possible (and recommended) to declare these requirements
              in the test <tt>Jamfile</tt> so that the tests aren't run, to
              conserve test resources, as given in the example below:</p>
              <pre>
import testing ;
import ../../config/checks/config : requires ;

project : requirements [ requires cxx11_variadic_templates cxx11_template_aliases ] ;

run cpp11_test.cpp ;
</pre>

              <p>For more information, see the <a href=
              "../libs/config/doc/html/boost_config/build_config.html">documentation
              of Boost.Config</a>.</p>

              <h4>Building Documentation</h4>

              <p>The library needs to provide a Boost Build project for
              building the documentation for the library. The
              <tt>project-root/doc</tt> project is the only location refered
              to by the top level documentation build scripts and the release
              building scripts. The documentation build project must have the
              following two features:</p>

              <ol>
                <li>Define a <tt>boostdoc</tt> target. This target should
                likely be an alias that looks roughly like:<br />
                  <pre>
alias boostdoc : my_boostbook_target
    : : : &lt;implicit-dependency&gt;my_boostbook_target ;
</pre>But if your project doesn't integrate into the global documentation
book you can use an empty alias like:<br />
                  <pre>
alias boostdoc ;
</pre>
                </li>

                <li>The project must default to building standalone
                documentation if it has any. The release scripts build this
                default so as to guarantee all projects have up to date
                documentation.</li>
              </ol>

              <h2><a name="Guidelines" id="Guidelines"></a>Guidelines</h2>

              <p>Please use these guidelines as a checklist for preparing the
              content a library submission. Not every guideline applies to
              every library, but a reasonable effort to comply is
              expected.</p>

              <h3><a name="Backwards_compatibility" id=
              "Backwards_compatibility"></a>Backwards Compatibility</h3>

              Boost libraries generally have a large and diverse user base.
              To ensure successful transitions from old APIs to newer APIs
              under those circumstances, library authors are encouraged to
              follow a few guidelines when introducing breaking changes in
              their library:

              <ol>
                <li>
                  Non-breaking changes can be done without restriction.
                </li>
                <li>
                  Small breaking changes can be made, but users should be
                  given notice a few releases before the change is published.
                  Most breaking changes fall into this category.
                </li>
                <li>
                  For large breaking changes <it>with</it> a migration path from
                  the old API to the new API (for example <tt>boost::filesystem</tt>
                  v2 to v3), the new API should be introduced in a separate
                  directory/namespace, and users should be noticed and given
                  a few releases to move over. The old API can be removed after
                  some time.
                </li>
                <li>
                  For large breaking changes <it>without</it> a migration path
                  (for example <tt>boost::spirit</tt> v2 to v3), the new API
                  should be provided in a separate directory/namespace, and the
                  old API should be preserved (because there's no migration path).
                  Removing the API should be considered the same as removing a
                  Boost library, which can be done but needs a more extensive
                  deprecation period.
                </li>
                <li>
                  Large breaking changes that are equivalent to a redesign or
                  rewrite of the library should be treated as a new library
                  and a formal review (or at least a mini review) is encouraged.
                </li>
              </ol>

              <h3><a name="Design_and_Programming" id=
              "Design_and_Programming"></a>Design and Programming</h3>

              <p>Aim first for clarity and correctness; optimization should
              be only a secondary concern in most Boost libraries.</p>

              <p>Aim for ISO Standard C++. Than means making effective use of
              the standard features of the language, and avoiding
              non-standard compiler extensions. It also means using the C++
              Standard Library where applicable.</p>

              <p>Headers should be good neighbors. See the <a href=
              "./header.html">header policy</a>. See <a href=
              "#Naming_consistency">Naming consistency</a>.</p>

              <p>Follow quality programming practices. See, for example,
              "Effective C++" 2nd Edition, and "More Effective C++", both by
              Scott Meyers, published by Addison Wesley.</p>

              <p>Use the C++ Standard Library or other Boost libraries, but
              only when the benefits outweigh the costs. Do not use libraries
              other than the C++ Standard Library or Boost. See <a href=
              "./reuse.html">Library reuse</a>.</p>

              <p>Read <a href=
              "../community/implementation_variations.html">Implementation
              Variation</a> to see how to supply performance, platform, or
              other implementation variations.</p>

              <p>Browse through <a href=
              "https://svn.boost.org/trac/boost/wiki/BestPracticeHandbook">the
              Best Practices Handbook</a> for ideas and links to source code
              in existing Boost libraries.</p>

              <p>Read the <a href="./separate_compilation.html">guidelines
              for libraries with separate source</a> to see how to ensure
              that compiled link libraries meet user expectations.</p>

              <p>Use the naming conventions of the C++ Standard Library (See
              <a href="#Naming">Naming conventions rationale</a>):</p>

              <ul>
                <li>Names (except as noted below) should be all lowercase,
                with words separated by underscores.</li>

                <li>Acronyms should be treated as ordinary names (e.g.
                <code>xml_parser</code> instead of
                <code>XML_parser</code>).</li>

                <li>Template parameter names begin with an uppercase
                letter.</li>

                <li>Macro (gasp!) names all uppercase and begin with
                BOOST_.</li>
              </ul>

              <p>Choose meaningful names - explicit is better than implicit,
              and readability counts. There is a strong preference for clear
              and descriptive names, even if lengthy.</p>

              <p>Use exceptions to report errors where appropriate, and write
              code that is safe in the face of exceptions.</p>

              <p>Avoid exception-specifications. See <a href=
              "#Exception-specification">exception-specification
              rationale</a>.</p>

              <p>Provide sample programs or confidence tests so potential
              users can see how to use your library.</p>

              <p>Provide a regression test program or programs which follow
              the <a href="./test.html">Test Policies and Protocols</a>.</p>

              <p>Although some boost members use proportional fonts, tabs,
              and unrestricted line lengths in their own code, boost's widely
              distributed source code should follow more conservative
              guidelines:</p>

              <ul>
                <li>Use fixed-width fonts. See <a href="#code_fonts">fonts
                rationale</a>.</li>

                <li>Use spaces rather than tabs. See <a href="#Tabs">tabs
                rationale</a>.</li>

                <li>Limit line lengths to 80 characters.</li>
              </ul>

              <p>End all documentation files (HTML or otherwise) with a
              copyright message and a licensing message. See the <a href=
              "../users/license.html">license information</a> page for the
              preferred form.</p>

              <p>Begin all source files (including programs, headers,
              scripts, etc.) with:</p>

              <ul>
                <li>A comment line describing the contents of the file.</li>

                <li>Comments describing copyright and licensing: again, the
                preferred form is indicated in the <a href=
                "../users/license.html">license information</a> page</li>

                <li>Note that developers are allowed to provide a copy of
                the license text in <code>LICENSE_1_0.txt</code>,
                <code>LICENSE.txt</code> or <code>LICENSE</code>
                file within repositories of their libraries.</li>

                <li>A comment line referencing your library on the Boost web
                site. For example:
                  <pre>
// See https://www.boost.org/libs/foo for library home page.
</pre>

                  <p>Where <code>foo</code> is the directory name (see below)
                  for the library. As well as aiding users who come across a
                  Boost file detached from its documentation, some of Boost's
                  automatic tools depend on this comment to identify which
                  library header files belong to.</p>
                </li>
              </ul>

              <p><strong>Assertions:</strong> If you want to add runtime
              assertions to your code (you should!), avoid C's
              <code>assert</code> macro and use Boost's
              <code>BOOST_ASSERT</code> macro (in
              <code>boost/assert.hpp</code> ) instead. It is more
              configurable. Use <code>BOOST_ASSERT</code> in public headers
              and in library source code (for separately compiled libraries).
              Use of C's <code>assert</code> macro is ok in examples and in
              documentation.</p>

              <p>Make sure your code compiles in the presence of the
              <code>min()</code> and <code>max()</code> macros. Some platform
              headers define <code>min()</code> and <code>max()</code> macros
              which cause some common C++ constructs to fail to compile. Some
              simple tricks can protect your code from inappropriate macro
              substitution:</p>

              <ul>
                <li>If you want to call <code>std::min()</code> or
                <code>std::max()</code>:

                  <ul>
                    <li>If you do not require argument-dependent look-up, use
                    <code>(std::min)(a,b)</code>.</li>

                    <li>If you do require argument-dependent look-up, you
                    should:

                      <ul>
                        <li><code>#include
                        &lt;boost/config.hpp&gt;</code></li>

                        <li>Use <code>BOOST_USING_STD_MIN();</code> to bring
                        <code>std::min()</code> into the current scope.</li>

                        <li>Use <code>min BOOST_PREVENT_MACRO_SUBSTITUTION
                        (a,b);</code> to make an argument-dependent call to
                        <code>min(a,b)</code>.</li>
                      </ul>
                    </li>
                  </ul>
                </li>

                <li>If you want to call
                <code>std::numeric_limits&lt;int&gt;::max()</code>, use
                <code>(std::numeric_limits&lt;int&gt;::max)()</code>
                instead.</li>

                <li>If you want to call a <code>min()</code> or
                <code>max()</code> member function, instead to doing
                <code>obj.min()</code>, use <code>(obj.min)()</code>.</li>

                <li>If you want to declare or define a function or a member
                function named <code>min</code> or <code>max</code>, then you
                must use the <code>BOOST_PREVENT_MACRO_SUBSTITUTION</code>
                macro. Instead of writing <code>int min() { return 0;
                }</code> you should write <code>int min
                BOOST_PREVENT_MACRO_SUBSTITUTION () { return 0; }</code> This
                is true regardless if the function is a free (namespace
                scope) function, a member function or a static member
                function, and it applies for the function declaration as well
                as for the function definition.</li>
              </ul>

              <h3><a name="Directory_structure" id="Directory_structure"></a>
              <a name="Filenames" id="Filenames"></a>Filenames</h3>

              <p>Naming requirements ensure that file and directory names are
              relatively portable, including to ISO 9660:1999 (with
              extensions) and other relatively limited file systems.
              Superscript links are provided to detailed rationale for each
              choice.</p>

              <ul>
                <li>Names must contain only
                <strong>lowercase</strong><sup><a href=
                "#Filename_rationale_1">1</a></sup> ASCII letters
                (<code>'a'</code>-<code>'z'</code>), numbers
                (<code>'0'</code>-<code>'9'</code>), underscores
                (<code>'_'</code>), hyphens (<code>'-'</code>), and periods
                (<code>'.'</code>). Spaces are not allowed<sup><a href=
                "#Filename_rationale_2">2</a></sup>.</li>

                <li>Directory names must not contain periods
                (<code>'.'</code>)<sup><a href=
                "#Filename_Rationale_3">3</a></sup>.</li>

                <li>The first and last character of a file name must not be a
                period (<code>'.'</code>)<sup><a href=
                "#Filename_rationale_4">4</a></sup>.</li>

                <li>The first character of names must not be a hyphen
                (<code>'-'</code>)<sup><a href=
                "#Filename_rationale_5">5</a></sup>.</li>

                <li>The maximum length of directory and file names is 31
                characters<sup><a href=
                "#Filename_rationale_6">6</a></sup>.</li>

                <li>The total path length must not exceed 207
                characters<sup><a href=
                "#Filename_rationale_7">7</a></sup>.</li>
              </ul>

              <p>Other conventions ease communication:</p>

              <ul>
                <li>Files intended to be processed by a C++ compiler as part
                of a translation unit should have <strong>a three-letter
                filename extension ending in "pp"</strong>. Other files
                should <i>not</i> use extensions ending in "pp". This
                convention makes it easy to identify all of the C++ source in
                Boost.</li>

                <li>All libraries have at their highest level a primary
                directory named for the particular library. See <a href=
                "#Naming_consistency">Naming consistency</a>. The primary
                directory may have sub-directories.</li>
              </ul>

              <h4><a name="Redirection" id="Redirection"></a>Redirection</h4>

              <p>The primary directory should always contain a file named
              index.html. Authors have requested this so that they can
              publish URL's in the form
              <i>https://www.boost.org/libs/lib-name</i> with the assurance a
              documentation reorganization won't invalidate the URL. Boost's
              internal tools are also simplified by knowing that a library's
              documentation is always reachable via the simplified URL.</p>

              <p>The primary directory <code>index.html</code> file should
              just do an automatic redirection to the <code>doc/html</code>
              subdirectory:</p>
              <pre>
&lt;!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"&gt;

&lt;html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"&gt;
&lt;head&gt;
  &lt;title&gt;Boost.<var>Name</var> Documentation&lt;/title&gt;
  &lt;meta http-equiv="Content-Type" content="text/html; charset=us-ascii" /&gt;
  &lt;meta http-equiv="refresh" content="0; URL=doc/html/index.html" /&gt;
&lt;/head&gt;

&lt;body&gt;
  Automatic redirection failed, please go to &lt;a href=
  "doc/index.html"&gt;doc/index.html&lt;/a&gt;
&lt;/body&gt;
&lt;/html&gt;
</pre>

              <h3><a name="Naming_consistency" id=
              "Naming_consistency"></a>Naming consistency</h3>

              <p>As library developers and users have gained experience with
              Boost, the following consistent naming approach has come to be
              viewed as very helpful, particularly for larger libraries that
              need their own header subdirectories and namespaces.</p>

              <p>Here is how it works. The library is given a name that
              describes the contents of the library. Cryptic abbreviations
              are strongly discouraged. Following the practice of the C++
              Standard Library, names are usually singular rather than
              plural. For example, a library dealing with file systems might
              chose the name "filesystem", but not "filesystems", "fs" or
              "nicecode".</p>

              <ul>
                <li>The library's primary directory (in parent
                <var>boost-root/libs</var>) is given that same name. For
                example, <var>boost-root/libs/filesystem</var>.</li>

                <li>The library's primary header directory (in
                <var>boost-root/libs/name/include</var>) is given that same
                name. For example,
                <var>boost-root/libs/filesystem/boost/filesystem</var>.</li>

                <li>The library's primary namespace (in parent
                <em>::boost</em>) is given that same name, except when
                there's a component with that name (e.g.,
                <em>boost::tuple</em>), in which case the namespace name is
                pluralized. For example, <em>::boost::filesystem</em>.</li>
              </ul>

              <p>When documenting Boost libraries, follow these conventions
              (see also the following section of this document):</p>

              <ul>
                <li>The library name is set in roman type.</li>

                <li>The library name is capitalized.</li>

                <li>A period between "Boost" and the library name (e.g.,
                Boost.Bind) is used if and only if the library name is not
                followed by the word "library".</li>

                <li>The word "library" is not part of the library name and is
                therefore lowercased.</li>
              </ul>

              <p>Here are a few examples of how to apply these
              conventions:</p>

              <ul>
                <li>Boost.Bind was written by Peter Dimov.</li>

                <li>The Boost Bind library was written by Peter Dimov.</li>

                <li>I regularly use Bind, a Boost library written by Peter
                Dimov.</li>
              </ul>

              <h3><a name="Documentation" id=
              "Documentation"></a>Documentation</h3>

              <p>Even the simplest library needs some documentation; the
              amount should be proportional to the need. The documentation
              should assume the readers have a basic knowledge of C++, but
              are not necessarily experts.</p>

              <p>The format for documentation should be HTML, and should not
              require an advanced browser or server-side extensions. Style
              sheets are acceptable. ECMAScript/JavaScript is discouraged.
              The documentation entry point should always be a file named
              index.html; see <a href="#Redirection">Redirection</a>.</p>

              <p>There is no single right way to do documentation. HTML
              documentation is often organized quite differently from
              traditional printed documents. Task-oriented styles differ from
              reference oriented styles. In the end, it comes down to the
              question: Is the documentation sufficient for the mythical
              "average" C++ programmer to use the library successfully?</p>

              <p>Appropriate topics for documentation often include:</p>

              <ul>
                <li>General introduction to the library. The introduction
                particularly needs to include:

                  <ul>
                    <li>A very high-level overview of what the library is
                    good for, and perhaps what it isn't good for,
                    understandable even by those with no prior knowledge of
                    the problem domain.</li>

                    <li>The simplest possible ("hello world") example of
                    using the library.</li>
                  </ul>
                </li>

                <li>Tutorial covering basic use cases.</li>

                <li>Reference documentation:

                  <ul>
                    <li>Description of each class.</li>

                    <li>Relationship between classes.</li>

                    <li>For each function, as applicable, description,
                    requirements (preconditions), effects, post-conditions,
                    returns, and throws.</li>

                    <li>Discussion of error detection and recovery
                    strategy.</li>
                  </ul>
                </li>

                <li>How to compile and link.</li>

                <li>How to test.</li>

                <li>Version or revision history.</li>

                <li>Rationale for design decisions. See <a href=
                "#Rationale">Rationale rationale</a>.</li>

                <li>Acknowledgements. See <a href=
                "#Acknowledgements">Acknowledgments rationale.</a></li>
              </ul>

              <p>If you need more help with how to write documentation you
              can check out the article on <a href=
              "../doc/libs/release/more/writingdoc/index.html">Writing
              Documentation for Boost</a>.</p>

              <h2><a name="Rationale" id="Rationale"></a>Rationale</h2>

              <p>Rationale for some of the requirements and guidelines
              follows.</p>

              <h3><a name="Exception-specification" id=
              "Exception-specification"></a>Exception-specification
              rationale</h3>

              <p>Exception specifications [ISO 15.4] are sometimes coded to
              indicate what exceptions may be thrown, or because the
              programmer hopes they will improve performance. But consider
              the following member from a smart pointer:</p>
              <pre>
T&amp; operator*() const throw()  { return *ptr; }
</pre>

              <p>This function calls no other functions; it only manipulates
              fundamental data types like pointers Therefore, no runtime
              behavior of the exception-specification can ever be invoked.
              The function is completely exposed to the compiler; indeed it
              is declared inline Therefore, a smart compiler can easily
              deduce that the functions are incapable of throwing exceptions,
              and make the same optimizations it would have made based on the
              empty exception-specification. A "dumb" compiler, however, may
              make all kinds of pessimizations.</p>

              <p>For example, some compilers turn off inlining if there is an
              exception-specification. Some compilers add try/catch blocks.
              Such pessimizations can be a performance disaster which makes
              the code unusable in practical applications.</p>

              <p>Although initially appealing, an exception-specification
              tends to have consequences that require <strong>very</strong>
              careful thought to understand. The biggest problem with
              exception-specifications is that programmers use them as though
              they have the effect the programmer would like, instead of the
              effect they actually have.</p>

              <p>A non-inline function is the one place a "throws nothing"
              exception-specification may have some benefit with some
              compilers.</p>

              <h3><a name="Naming" id="Naming"></a>Naming conventions
              rationale</h3>

              <p>The C++ standard committee's Library Working Group discussed
              this issue in detail, and over a long period of time. The
              discussion was repeated again in early boost postings. A short
              summary:</p>

              <ul>
                <li>Naming conventions are contentious, and although several
                are widely used, no one style predominates.</li>

                <li>Given the intent to propose portions of boost for the
                next revision of the C++ standard library, boost decided to
                follow the standard library's conventions.</li>

                <li>Once a library settles on a particular convention, a vast
                majority of stakeholders want that style to be consistently
                used.</li>
              </ul>

              <h3><a name="code_fonts" id="code_fonts"></a>Source code fonts
              rationale</h3>

              <p>Dave Abrahams comments: An important purpose (I daresay the
              primary purpose) of source code is communication: the
              documentation of intent. This is a doubly important goal for
              boost, I think. Using a fixed-width font allows us to
              communicate with more people, in more ways (diagrams are
              possible) right there in the source. Code written for
              fixed-width fonts using spaces will read reasonably well when
              viewed with a variable-width font, and as far as I can tell
              every editor supporting variable-width fonts also supports
              fixed width. I don't think the converse is true.</p>

              <h3><a name="Tabs" id="Tabs"></a>Tabs rationale</h3>

              <p>Tabs are banned because of the practical problems caused by
              tabs in multi-developer projects like Boost, rather than any
              dislike in principle. See <a href=
              "../community/groups.html#archive">mailing list archives</a>.
              Problems include maintenance of a single source file by
              programmers using tabs and programmers using spaces, and the
              difficulty of enforcing a consistent tab policy other than just
              "no tabs". Discussions concluded that Boost files should either
              all use tabs, or all use spaces, and thus the decision to stick
              with spaces for indentation.</p>

              <h3><a name="FileNamesRat" id="FileNamesRat"></a>Directory and
              File Names rationale</h3>

              <p><a name="Filename_rationale_1" id=
              "Filename_rationale_1">1</a>. Some legacy file systems require
              single-case names. Single-case names eliminate casing mistakes
              when moving from case-insensitive to case-sensitive file
              systems.</p>

              <p><a name="Filename_rationale_2" id=
              "Filename_rationale_2">2</a>. This is the lowercase portion of
              the POSIX portable filename character set. To quote the POSIX
              standard, "Filenames should be constructed from the portable
              filename character set because the use of other characters can
              be confusing or ambiguous in certain contexts."</p>

              <p><a name="Filename_Rationale_3" id=
              "Filename_Rationale_3">3</a>. Strict implementations of ISO
              9660:1999 and some legacy operating systems prohibit dots in
              directory names. The need for this restriction is fading, and
              it will probably be removed fairly soon.</p>

              <p><a name="Filename_rationale_4" id=
              "Filename_rationale_4">4</a>. POSIX has special rules for names
              beginning with a period. Windows prohibits names ending in a
              period.</p>

              <p><a name="Filename_rationale_5" id=
              "Filename_rationale_5">5</a>. Would be too confusing or
              ambiguous in certain contexts.</p>

              <p><a name="Filename_rationale_6" id=
              "Filename_rationale_6">6</a>. We had to draw the line
              somewhere, and so the limit imposed by a now obsolete Apple
              file system was chosen years ago. It still seems a reasonable
              limit to aid human comprehension.</p>

              <p><a name="Filename_rationale_7" id=
              "Filename_rationale_7">7</a>. ISO 9660:1999.</p>

              <h3><a name="JavaScript" id=
              "JavaScript"></a>ECMAScript/JavaScript rationale</h3>

              <p>Before the 1.29.0 release, two Boost libraries added
              ECMAScript/JavaScript documentation. Controversy followed (see
              <a href="../community/groups.html#archive">mailing list
              archives</a>), and the developers were asked to remove the
              ECMAScript/JavaScript. Reasons given for banning included:</p>

              <ul>
                <li>Incompatible with some older browsers and some text based
                browsers.</li>

                <li>Makes printing docs pages difficult.</li>

                <li>Often results in really bad user interface design.</li>

                <li>"It's just annoying in general."</li>

                <li>Would require Boost to test web pages for
                ECMAScript/JavaScript compliance.</li>

                <li>Makes docs maintenance by other than the original
                developer more difficult.</li>
              </ul>

              <p>Please conside those reasons if you decide that JavaScript
              is something you must use. In particular please keep in mind
              that the Boost community is not responsible for testing your
              use of JavaScript. And hence it is up to you to ensure that the
              above issues are fully resolved in your use case.</p>

              <p>ECMAScript/JavaScript use is allowed but discouraged for the
              reasons above.</p>

              <h3><a name="Rationale_rationale" id=
              "Rationale_rationale"></a>Rationale rationale</h3>

              <p>Rationale is defined as "The fundamental reasons for
              something; basis" by the American Heritage Dictionary.</p>

              <p>Beman Dawes comments: Failure to supply contemporaneous
              rationale for design decisions is a major defect in many
              software projects. Lack of accurate rationale causes issues to
              be revisited endlessly, causes maintenance bugs when a
              maintainer changes something without realizing it was done a
              certain way for some purpose, and shortens the useful lifetime
              of software.</p>

              <p>Rationale is fairly easy to provide at the time decisions
              are made, but very hard to accurately recover even a short time
              later.</p>

              <h3><a name="Acknowledgements" id=
              "Acknowledgements"></a>Acknowledgements rationale</h3>

              <p>As a library matures, it almost always accumulates
              improvements suggested to the authors by other boost members.
              It is a part of the culture of boost.org to acknowledge such
              contributions, identifying the person making the suggestion.
              Major contributions are usually acknowledged in the
              documentation, while minor fixes are often mentioned in
              comments within the code itself.</p>
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